JP4626343B2 - Polybutylene terephthalate pellets, compound products and molded articles thereof, and methods for producing the same - Google Patents

Description

  The present invention relates to a polybutylene terephthalate pellet, a compound product and a molded product thereof, and a method for producing the same, and more particularly, a polybutylene terephthalate pellet having excellent color tone, hydrolysis resistance and transparency, reduced foreign matter, and improved productivity. The present invention relates to butylene terephthalate pellets, compound products and molded products thereof, and methods for producing them. Hereinafter, polybutylene terephthalate may be abbreviated as PBT.

  PBT, which is a representative engineering plastic among thermoplastic polyester resins, is easy to process, mechanical properties, heat resistance, chemical resistance, aroma retention (flavor barrier properties), and other physical and chemical properties. Because of its excellent characteristics, it is widely used in injection molded products such as automobile parts, electrical / electronic parts, precision equipment parts. In recent years, taking advantage of its excellent properties, it has been widely used in the fields of films, sheets, filaments and the like. In these applications, since a product is generally obtained by extrusion molding, a higher molecular weight PBT is required as compared with injection molding.

  In general, PBT performs terephthalic acid or its ester-forming derivative and 1,4-butanediol using a catalyst to carry out melt polycondensation through an esterification reaction or a transesterification reaction, and solid-phase polymerization as necessary. Manufactured. By the way, when PBT is exposed to a high temperature for a long time, there is a problem in that the deterioration progresses and the color tone deteriorates and the terminal carboxyl group concentration increases. And since the heat history at the time of manufacture receives so much that PBT becomes high molecular weight, in the melt polymerization, said problem is so remarkable that PBT with high intrinsic viscosity.

  In order to solve the above problems, a method is widely employed in which melt polymerization is performed at a relatively low temperature and in a short time, and then solid phase polymerization is performed at a temperature below the melting point. Solid-phase polymerization is an excellent polymerization method from the viewpoint of color tone improvement and terminal carboxyl group concentration reduction. However, it has problems such as long polymerization time, large energy loss, and excessive equipment. Yes. In addition, solid phase polymerization is usually carried out in the form of cylindrical or spherical pellets, but the surface layer portion where low molecular weight components generated by polymerization tend to volatilize tends to be high in molecular weight, and the molecular weight is difficult to increase in the central portion. Therefore, a viscosity difference is generated in the pellet. This viscosity difference causes unevenness when the pellets are melted in the extruder or molding machine, causing not only an increase in the load on the screw drive motor, but also its fluctuations, which in turn causes fluctuations in product quality. It has become a production problem.

  Further, when the viscosity difference in the pellet is large, the high molecular weight portion and the low molecular weight portion are not sufficiently mixed, and there is a problem that foreign matter (fish eye) is likely to occur. Such problems are that new applications for PBT such as films, sheets and filaments generally use screws with a low kneading effect during molding, and other than resin products compared to compound product applications in which PBT has been widely used. This is facilitated by the small amount of fillers and additives.

  The above foreign matter is a serious problem because the commercial value is remarkably reduced in a film or sheet, and the filament is broken at the time of molding based on this. In these applications, PBT having a high molecular weight is required as described above, and it is necessary to further advance the solid-phase polymerization reaction. As a result, the difference in viscosity between the pellet surface layer and the central portion tends to increase more and more. The issue of fisheye is more closely highlighted.

  In order to solve the above problem, a film in which the amount of fish eye is suppressed to a specific amount or less by removing the fish eye causative substance with a filter installed in the polymerization process without performing solid phase polymerization has been proposed ( For example, Patent Document 1).

  However, since a large amount of titanium catalyst is used in the conventional production method, there is a problem that the life of the filter is remarkably short as a result of some of these being deactivated and precipitated. Further, the catalyst remaining in the PBT promotes a reaction involving the increase in the terminal carboxyl group concentration of the PBT and coloring, and causes thermal deterioration of the PBT. Such thermal degradation occurs not only due to the heat history during PBT production but also due to the heat history during kneading and molding. Therefore, from the viewpoint of preventing thermal degradation, it is preferable to lower the temperature as much as possible during polymerization, kneading and molding, but if the temperature during polymerization is lowered to obtain PBT having the same molecular weight, the polymerization time is lengthened. In the end, the problem remains unresolved from a thermal history perspective.

  On the other hand, if the amount of the catalyst is increased, the polymerization time can be shortened at a low temperature to obtain a PBT having the same molecular weight. However, since the catalyst promotes the increase of foreign matter, coloring and deterioration as described above, this method is eventually used. However, it is not possible to obtain a good quality product.

  The problems of the above prior art can be summarized as follows. That is, if the amount of catalyst is lowered, the polymerization temperature is lowered, and the polymerization time is shortened, only low molecular weight PBT is inevitably obtained. If a high molecular weight PBT is obtained while suppressing thermal degradation, solid phase polymerization is achieved. There is no choice but to do. However, PBT subjected to solid-phase polymerization has the above-described fluctuations during melt extrusion and the problem of fish eye generation. Especially when the molding temperature is lowered to prevent thermal deterioration even during kneading or molding, Since it becomes difficult to mix the high molecular weight component of the pellet surface layer portion and the low molecular weight region of the central portion, there is a dilemma that these problems become large.

  Furthermore, in recent years, PBT has been widely used for food packaging films and the like, but at the end of PBT, in addition to hydroxyl groups and carboxyl groups, methoxycarbonyl groups derived from raw materials remain. Such a group generates methanol and its oxides formaldehyde and formic acid by heat during molding, heating by a microwave oven, enzymes, acids and bases contained in food, It has caused toxicity problems. In addition, formic acid is a cause of damaging metal polymerization equipment, molding equipment, vacuum related equipment, etc., and its reduction is required.

JP 2003-73488 A

  The present invention has been made in view of the above circumstances, and its purpose is to provide a PBT pellet for producing a molded article having excellent color tone, hydrolysis resistance, transparency, molding stability and reduced foreign matter. There is to do.

  As a result of intensive studies, the present inventor has found that the content of the titanium catalyst and the terminal methoxycarbonyl group concentration are below a specific value, and the difference in intrinsic viscosity between the center portion and the surface layer portion of the pellet is below a specific value. It has been found that the above problem can be easily solved by PBT, and the present invention has been completed.

That is, the first gist of the present invention is that it contains titanium and the amount thereof is 90 ppm by weight or less as titanium atoms, the terminal methoxycarbonyl group concentration is 0.5 μeq / g or less , and the solution haze is 5% or less . It is a pellet made of polybutylene terephthalate, the average intrinsic viscosity of the pellet is 0.90 to 2.00 dL / g, and the difference in intrinsic viscosity between the center part and the surface layer part of the pellet is 0.10 dL / g or less It exists in the polybutylene terephthalate pellet characterized by these.
(However, the solution haze is the turbidity value of a solution obtained by dissolving 2.7 g of polybutylene terephthalate in 20 mL of a phenol / tetrachloroethane mixed solution (weight ratio 3/2).)

  The second gist of the present invention resides in a compound product comprising the above-mentioned polybutylene terephthalate pellets as at least a part of the raw material, and the third gist of the present invention is at least one of the raw materials. As a part, the present invention resides in a method for producing a compound product using the above polybutylene terephthalate pellets and kneading using an extruder.

  A fourth gist of the present invention lies in a molded product characterized by using the above-described compound product as at least a part of the molding material, and a fifth gist of the present invention is at least one of the molding material. The present invention resides in a method for producing a molded product, characterized in that the above-described compound product is used as a part and molding is performed using an injection molding machine.

  The sixth gist of the present invention resides in a molded product characterized by using the above-mentioned polybutylene terephthalate pellets as at least a part of the raw material. At least in part, the present invention resides in a method for producing a molded product, characterized in that the above polybutylene terephthalate pellets are used and molded using an extruder.

  According to the present invention, it is possible to provide a PBT molded article excellent in color tone, hydrolysis resistance, transparency and molding stability and having reduced foreign matters, and a method for producing the same.

  Hereinafter, the present invention will be described in detail. However, the description of the constituent elements described below is a representative example of embodiments of the present invention, and the present invention is not limited to these contents.

  In the present invention, PBT has a structure in which a terephthalic acid unit and a 1,4-butanediol unit are ester-bonded, 50 mol% or more of dicarboxylic acid units are composed of terephthalic acid units, and 50 mol% or more of diol units. Refers to a polyester comprising 1,4-butanediol units. The proportion of terephthalic acid units in all dicarboxylic acid units is preferably 70 mol% or more, more preferably 80 mol% or more, particularly preferably 95 mol% or more, and 1,4-butanediol unit in all diol units. The ratio is preferably 70 mol% or more, more preferably 80 mol% or more, and particularly preferably 95 mol% or more. When the amount of terephthalic acid units or 1,4-butanediol units is less than 50 mol%, the crystallization rate of PBT is lowered, and the moldability is deteriorated.

  In the present invention, the dicarboxylic acid component other than terephthalic acid is not particularly limited. For example, phthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,4′-benzophenone Aromatic dicarboxylic acids such as dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3- Aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid I can list them. These dicarboxylic acid components can be introduced into the polymer skeleton using a dicarboxylic acid or a dicarboxylic acid derivative such as a dicarboxylic acid ester or a dicarboxylic acid halide as a raw material.

  In the present invention, the diol component other than 1,4-butanediol is not particularly limited. For example, ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, polytetra Methylene glycol, dibutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, aliphatic diols such as 1,8-octanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol , 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol and other alicyclic diols, xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane, bis ( 4- And aromatic diols such as hydroxyphenyl) sulfone.

  In the present invention, hydroxycarboxylic acids such as lactic acid, glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, p-β-hydroxyethoxybenzoic acid, and alkoxycarboxylic acids. Monofunctional components such as acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarbaric acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane Trifunctional or polyfunctional components such as trimethylolpropane, glycerol and pentaerythritol can be used as the copolymerization component.

  The PBT of the present invention is obtained using 1,4-butanediol and terephthalic acid (or dialkyl terephthalate) as raw materials and using a titanium compound as a catalyst.

  Specific examples of the titanium catalyst include inorganic titanium compounds such as titanium oxide and titanium tetrachloride, titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate. Among these, tetraalkyl titanate is preferable, and among them, tetrabutyl titanate is preferable.

  In addition to titanium, tin may be used as a catalyst. Tin is usually used as a tin compound, and specific examples thereof include dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, triethyltin hydroxide. , Triphenyltin hydroxide, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin sulfide, butylhydroxytin oxide, methylstannic acid, ethylstannic acid, butylstannic acid Is mentioned.

  Since tin deteriorates the color tone of PBT, the amount added is usually 200 ppm by weight or less, preferably 100 ppm by weight or less, more preferably 10 ppm by weight or less, and preferably not added as tin atoms.

  In addition to titanium, magnesium compounds such as magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium alkoxide In addition to calcium compounds such as calcium hydrogen phosphate, antimony compounds such as antimony trioxide, germanium compounds such as germanium dioxide and germanium tetroxide, manganese compounds, zinc compounds, zirconium compounds, cobalt compounds, orthophosphoric acid, phosphorous acid, hypochlorous acid Reaction aids such as phosphoric acid, polyphosphoric acid, phosphorus compounds such as esters and metal salts thereof, sodium hydroxide and sodium benzoate may be used.

  One of the features of the PBT of the present invention is that it contains titanium and the amount thereof is 90 ppm by weight or less as titanium atoms. The above value is the weight ratio of atoms to PBT.

  In the present invention, the lower limit of the titanium content is usually 10 ppm by weight, preferably 15 ppm by weight, more preferably 20 ppm by weight, particularly preferably 25 ppm by weight, and the upper limit is preferably 80 ppm by weight, 70 ppm by weight, more preferably 50 ppm by weight, particularly preferably 40 ppm by weight, particularly 33 ppm by weight is preferred. When the titanium content exceeds 90 ppm by weight, hydrolysis resistance due to deterioration of color tone or increase in terminal carboxyl group concentration due to thermal history when forming PBT or kneading, film or sheet In addition to incurring deterioration in properties, the fish eye derived from the catalyst residue is increased, particularly when the catalyst is deactivated. On the other hand, when the amount is too small, the polymerizability of PBT is deteriorated, and as a result, it is necessary to raise the polymerization temperature, resulting in deterioration of color tone and hydrolysis resistance.

  The metal content such as titanium atom can be measured using a method such as atomic emission, atomic absorption, Inductively Coupled Plasma (ICP) after recovering the metal in the polymer by a method such as wet ashing.

  The terminal carboxyl group concentration of the PBT of the present invention is usually 0.1 to 50 μeq / g, preferably 1 to 40 μeq / g, more preferably 5 to 30 μeq / g, and particularly preferably 10 to 25 μeq / g. If the terminal carboxyl group concentration is too high, the hydrolysis resistance may deteriorate. Moreover, while the carboxyl group terminal of PBT tends to increase by the heat history at the time of shaping | molding of a film or a sheet, when it mixes with resin with few other carboxyl terminals, it is per unit weight of a film or a sheet. Although the terminal carboxyl group may decrease, the terminal carboxyl group concentration in the final product film or sheet is usually 0.1 to 50 μeq per unit weight of the film or sheet including the weight of other resins. / G, preferably 1 to 40 μeq / g, more preferably 5 to 30 μeq / g, and particularly preferably 10 to 25 μeq / g.

  The terminal carboxyl group concentration of PBT can be determined by dissolving PBT in an organic solvent and titrating the solution using an alkali solution such as a sodium hydroxide solution.

  Further, the terminal vinyl group concentration of the PBT of the present invention is usually 0.1 to 15 μeq / g, preferably 0.5 to 10 μeq / g, and more preferably 1 to 8 μeq / g. If the terminal vinyl group concentration is too high, the color tone is deteriorated. The terminal vinyl group concentration tends to further increase due to the heat history at the time of molding. Therefore, when the molding temperature is high or in the case of a production method having a recycling process, the color tone is further deteriorated.

  In addition to the hydroxyl group, carboxyl group, and vinyl group, a methoxycarbonyl group derived from the raw material may remain at the end of the PBT, particularly when dimethyl terephthalate is used as the raw material. . By the way, the methoxycarbonyl terminal generates methanol, formaldehyde, and formic acid due to heat generated during the formation of a film or sheet, and these toxicities are particularly problematic when used for food applications. In addition, formic acid may corrode metal molding equipment and vacuum related equipment. Therefore, the terminal methoxycarbonyl group concentration in the PBT of the present invention must be 0.5 μeq / g or less. The terminal methoxycarbonyl group concentration is preferably 0.3 μeq / g or less, more preferably 0.2 μeq / g or less, and particularly preferably 0.1 μeq / g or less.

The above terminal vinyl group concentration and terminal methoxycarbonyl group concentration can be quantified by dissolving PBT in a mixed solution of deuterated chloroform / hexafluoroisopropanol = 7/3 (volume ratio) and measuring ¹ H-NMR. I can do it. At this time, in order to prevent overlap with the solvent signal, a very small amount of a basic component such as heavy pyridine may be added.

  The average intrinsic viscosity of the PBT of the present invention should be from 0.90 to 2.00 dL / g. The average intrinsic viscosity is preferably 1.00 to 1.80 dL / g, more preferably 1.10 to 1.40, and particularly preferably 1.20 to 1.30 dLg. When the intrinsic viscosity is less than 0.90 dL / g, in the extrusion molding, the drawdown from the die tends to become severe, not only the moldability is deteriorated, but the mechanical strength of the molded product becomes insufficient. When it exceeds 00 dL / g, the melt viscosity increases, the fluidity deteriorates, and the moldability and the surface properties of the product tend to deteriorate. The intrinsic viscosity is a value measured at 30 ° C. using a mixed solution of phenol / tetrachloroethane (weight ratio 1/1) as a solvent. In the present invention, the average intrinsic viscosity refers to the intrinsic viscosity obtained by dissolving the whole pellet.

  The difference in intrinsic viscosity between the center portion and the surface layer portion of the PBT pellets of the present invention should be 0.10 dL / g or less. The difference in intrinsic viscosity is preferably 0.07 dL / g or less, more preferably 0.05 dL / g or less, and particularly preferably 0.03 dL / g or less. If the difference in intrinsic viscosity between the center of the pellet and the surface layer is greater than 0.10 dL / g, not only will it cause problems during molding, such as an increase in fish eyes and stretch failure, but also an increase in the torque load of the extruder. In addition, it causes torque fluctuations, leading to unstable product quality.

  In the present invention, the difference in intrinsic viscosity between the central part and the surface layer part of the pellet refers to the difference in intrinsic viscosity between two parts within 10% by weight from the central part and the outer peripheral part. The intrinsic viscosity of the center and the surface layer of the pellet is the fraction of the PBT solution in order from the surface of the pellet by repeating the operation of placing the pellet in a solvent in which PBT is soluble and replacing it with a fresh solvent over time. The solvent is removed from the first fraction at which the pellets have started to dissolve and the last fraction at which the pellets have completely dissolved, and PBT at the surface and the center of the pellet are obtained separately, and the respective intrinsic viscosities are measured. Can be obtained. In operation, in order to obtain a complete surface layer portion and a complete center portion, it is necessary to obtain an infinite number of fractions. Therefore, in the present invention, a fraction that is within 10% by weight from the center portion and the surface layer portion, , Defined as the surface layer.

  As long as the conditions of the present invention are satisfied, the production method of PBT is not limited. However, while suppressing deterioration in color tone and increase in terminal carboxyl group concentration, the fish eye is reduced and high molecular weight suitable for films, sheets and filaments. In order to obtain PBT, a method in which the amount of catalyst added is suppressed to 90 ppm by weight or less and melt polymerization is performed at a low temperature for a short time is generally preferable. When the melt polymerization is performed in a short time, it is difficult to obtain a high molecular weight PBT suitable for films, sheets and filaments. Therefore, as an example of a method for obtaining PBT suitable for the application of the present invention, there is a method of preventing deactivation of the catalyst, improving interface renewal at the time of polycondensation, and lowering the pressure.

When the catalyst is deactivated, precipitation occurs and the PBT haze increases. The solution haze of PBT used in the present invention is 5 % or less as a turbidity value of a solution obtained by dissolving 2.7 g of PBT in 20 mL of a mixed solution of phenol / tetrachloroethane (weight ratio 3/2), preferably It is 3% or less, more preferably 2% or less, and particularly preferably 1% or less. Haze resulting from catalyst deactivation causes deterioration of transparency of films, sheets, and filaments, and significantly impairs commercial value.

  Next, an example of a method for producing the PBT of the present invention by a direct polymerization method using terephthalic acid as a raw material will be described. The production method of PBT is roughly divided into a batch method and a continuous method, depending on the raw material supply or polymer discharge form. In addition to performing initial esterification reaction by continuous operation and subsequent polycondensation by batch operation, there is also a method of conversely performing initial esterification reaction by batch operation and subsequent polycondensation by continuous operation. . In the present invention, from the viewpoint of productivity and product quality stability, and the improvement effect of the present invention, a method of continuously supplying raw materials and continuously performing an esterification reaction is preferable. A so-called continuous method in which the reaction is continuously carried out is preferred.

  In the present invention, in the esterification reaction tank, at least a portion of 1,4-butanediol is supplied to the esterification reaction tank independently of terephthalic acid in the presence of a titanium catalyst, while terephthalic acid and 1,4 are added. A step of continuously esterifying with butanediol is preferably employed. That is, in the present invention, haze and foreign matters derived from the catalyst are reduced, and the catalytic activity is not lowered. Therefore, in addition to 1,4-butanediol supplied together with terephthalic acid as a raw slurry or solution, Independent of the acid, 1,4-butanediol is fed to the esterification reactor. Hereinafter, the 1,4-butanediol may be referred to as “separately supplied 1,4-butanediol”.

  The “separately supplied 1,4-butanediol” can be filled with fresh 1,4-butanediol independent of the process. In addition, “separately supplied 1,4-butanediol” collects 1,4-butanediol distilled from the esterification reaction tank with a condenser or the like and holds it in the reaction tank as it is or in a temporary tank. It can be refluxed, or can be supplied as 1,4-butanediol having a purity improved by separating and purifying impurities. Hereinafter, “separately supplied 1,4-butanediol” composed of 1,4-butanediol collected by a condenser or the like may be referred to as “recycled 1,4-butanediol”. From the viewpoint of effective utilization of resources and simplicity of equipment, it is preferable to apply “recycled 1,4-butanediol” to “separately supplied 1,4-butanediol”.

  In addition, 1,4-butanediol distilled from an esterification reaction tank is usually a component such as water, tetrahydrofuran (hereinafter abbreviated as “THF”), dihydrofuran, alcohol, etc., in addition to the 1,4-butanediol component. Is included. Therefore, it is preferable that the distillate 1,4-butanediol is separated and purified from components such as water and THF after being collected by a condenser or the like or collected, and then returned to the reaction vessel.

  In the present invention, it is preferable to return 10% by weight or more of “separately supplied 1,4-butanediol” directly to the reaction liquid phase part. Here, the reaction liquid phase part indicates the liquid phase side of the gas-liquid interface of the esterification reaction tank, and returning directly to the reaction liquid phase part means “separate supply 1, 4- This means that “butanediol” is supplied directly to the liquid phase part without going through the gas phase part. The ratio of returning directly to the liquid phase part of the reaction liquid is usually 30% by weight or more, preferably 50% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more. When the amount of “separately supplied 1,4-butanediol” returned directly to the reaction liquid phase is small, the titanium catalyst tends to be deactivated.

  The temperature of “separately supplied 1,4-butanediol” when returning to the reactor is usually 50 to 220 ° C., preferably 100 to 200 ° C., more preferably 150 to 190 ° C. When the temperature of “separately supplied 1,4-butanediol” is too high, the amount of by-product of THF tends to increase, and when it is too low, the heat load tends to increase, which tends to cause energy loss.

  In the present invention, in order to prevent deactivation of the catalyst, it is preferable to supply 10% by weight or more of the titanium catalyst used in the esterification reaction directly to the reaction liquid phase part independently of terephthalic acid. . Here, the reaction liquid phase portion refers to the liquid phase side of the gas-liquid interface of the esterification reaction tank, and supplying directly to the reaction liquid phase portion uses piping or the like, and the titanium catalyst is the gas in the reactor. This means that it is directly supplied to the liquid phase part without going through the phase part. The proportion of the titanium catalyst added directly to the reaction liquid phase is usually 30% by weight or more, preferably 50% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more.

  The titanium catalyst can be supplied directly to the reaction liquid phase part of the esterification reaction tank with or without being dissolved in a solvent or the like, but the supply amount is stabilized, and from the heating medium jacket of the reactor, etc. In order to reduce adverse effects such as heat denaturation, it is preferable to dilute with a solvent such as 1,4-butanediol. The concentration at this time is usually 0.01 to 20% by weight, preferably 0.05 to 10% by weight, more preferably 0.08 to 8% by weight, as the concentration of the titanium catalyst with respect to the whole solution. Further, from the viewpoint of reducing foreign matter, the water concentration in the solution is usually 0.05 to 1.0% by weight. The temperature for preparing the solution is usually 20 to 150 ° C., preferably 30 to 100 ° C., more preferably 40 to 80 ° C. from the viewpoint of preventing deactivation and aggregation. Moreover, it is preferable to mix a catalyst solution with a separate supply 1, 4- butanediol and piping etc., and supply to an esterification reaction tank from the point of deterioration prevention, precipitation prevention, and deactivation prevention.

  An example of the continuous method of the present invention is as follows. That is, the dicarboxylic acid component having terephthalic acid as a main component and the diol component having 1,4-butanediol as a main component are mixed in a raw material mixing tank to form a slurry, and in one or a plurality of esterification reaction tanks In the presence of a titanium catalyst, the esterification reaction is continuously carried out, and the resulting oligomer as an esterification reaction product is transferred to a polycondensation reaction tank, and in the polycondensation reaction tank or tanks, the polycondensation catalyst The polycondensation reaction is preferably carried out continuously under stirring.

  The temperature of the esterification reaction is usually 180 to 260 ° C., preferably 200 to 245 ° C., more preferably 210 to 235 ° C., and the pressure (absolute pressure, hereinafter the same) is usually 10 to 133 kPa, preferably 13 to 101 kPa. More preferably, the reaction time is 60 to 90 kPa, and the reaction time is usually 0.5 to 10 hours, preferably 1 to 6 hours. The temperature of the polycondensation reaction is usually 210 to 280 ° C, preferably 220 to 265 ° C, more preferably 230 to 245 ° C, and the pressure is usually 27 kPa or less, preferably 20 kPa or less, more preferably 13 kPa or less, the reaction time. Is usually 2 to 15 hours, preferably 3 to 10 hours. At this time, a new catalyst may be added in the polycondensation stage, or the catalyst used in the esterification reaction may be used as it is as a polycondensation catalyst and no new catalyst may be added. The polymer obtained by the polycondensation reaction is usually transferred from the bottom of the polycondensation reaction tank to a polymer extraction die and extracted in the form of a strand, and while being cooled with water or after being cooled with water, it is cut with a cutter and pelletized.

  In the present invention, the molar ratio of terephthalic acid and 1,4-butanediol preferably satisfies the following formula (1).

  The above "1,4-butanediol supplied from the outside to the esterification reaction tank" refers to 1,4-butanediol supplied together with terephthalic acid as a raw slurry or solution, and independently supplied from these 1,4-butanediol, 1,4-butanediol used as a solvent for the catalyst, etc.

  When the above BM / TM value is smaller than 1.1, the conversion rate is lowered and the catalyst is deactivated. When it is larger than 5.0, not only the thermal efficiency is lowered but also by-products such as THF are increased. Tend to. The value of BM / TM is preferably 1.5 to 4.5, more preferably 2.0 to 4.0, and particularly preferably 3.1 to 3.8.

  In the present invention, the esterification reaction is preferably performed at a temperature equal to or higher than the boiling point of 1,4-butanediol in order to shorten the reaction time. The boiling point of 1,4-butanediol depends on the reaction pressure, but is 230 ° C. at 101.1 kPa (atmospheric pressure) and 205 ° C. at 50 kPa.

  As the esterification reaction tank, known ones can be used, which may be any type such as a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower type continuous reaction tank, etc. Alternatively, a plurality of tanks in which the same kind or different kinds of tanks are connected in series or in parallel may be used. Among them, a reaction tank having a stirring device is preferable, and as a stirring device, a turbine stator type high-speed rotating stirrer, a disk mill type stirrer, a rotor mill type stirrer in addition to a normal type including a power unit, a bearing, a shaft, and a stirring blade. A type that rotates at high speeds can also be used.

The form of stirring is not particularly limited, and in addition to the usual stirring method in which the reaction solution in the reaction tank is directly stirred from the top, bottom, side, etc. of the reaction tank, a part of the reaction solution is connected to the reactor by piping or the like. A method of circulating the reaction solution by taking it outside and stirring it with a line mixer or the like can also be employed.
Known types of stirring blades can be selected, and specific examples include propeller blades, screw blades, turbine blades, fan turbine blades, disk turbine blades, fiddler blades, full zone blades, and Max blend blades.

  In the production of PBT, usually, a plurality of reaction vessels are used, preferably 2 to 5 reaction vessels, and the molecular weight is sequentially increased. Usually, a polycondensation reaction is performed following the initial esterification reaction.

  In the polycondensation reaction step of PBT, a single reaction tank or a plurality of reaction tanks may be used, but a multistage reaction tank is preferably used. The form of the reaction tank may be any type such as a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower type continuous reaction tank, or the like. Among them, a reaction tank having a stirring device is preferable, and as a stirring device, a turbine stator type high-speed rotating stirrer, a disk mill type stirrer, a rotor mill type stirrer in addition to a normal type including a power unit, a bearing, a shaft, and a stirring blade. A type that rotates at high speeds can also be used.

  The form of stirring is not particularly limited, and in addition to the usual stirring method in which the reaction solution in the reaction tank is directly stirred from the top, bottom, side, etc. of the reaction tank, a part of the reaction solution is connected to the reactor by piping. A method of circulating the reaction solution by taking it outside and stirring it with a line mixer or the like can also be employed. In particular, it is recommended that at least one of the polycondensation reaction tanks use a horizontal reactor having a surface rotation axis in the horizontal direction and excellent self-cleaning properties.

  Further, in order to suppress coloring and deterioration and to suppress an increase in the end of vinyl group or the like, in at least one reaction tank, a high vacuum of usually 1.3 kPa or less, preferably 0.5 kPa or less, more preferably 0.3 kPa or less. The temperature is usually 225 to 255 ° C, preferably 230 to 250 ° C, more preferably 233 to 245 ° C.

  Further, the PBT polycondensation reaction step is to produce a PBT having a relatively small molecular weight by melt polycondensation, for example, an intrinsic viscosity of about 0.1 to 1.0, and then at a temperature below the melting point of the PBT. Although solid phase polymerization can be performed, as described above, in the present invention, the difference in intrinsic viscosity between the pellet surface layer portion and the central portion needs to be 0.10 dL / g or less.

  In the PBT of the present invention, foreign matters derived from the catalyst are drastically reduced. Therefore, it is not necessary to remove the foreign matters. However, by installing a filter in the polymer precursor or the polymer flow path, the quality can be further improved. An excellent polymer is obtained. In the present invention, for the reasons described above, when a filter having the same opening as that used in a conventional PBT manufacturing facility is used, it is possible to extend the life until the replacement. Further, if the life until replacement is set to be the same, a filter with a smaller opening can be installed.

  If the filter is installed too far upstream of the manufacturing process, foreign matter generated downstream cannot be removed, and the pressure loss of the filter increases and the flow rate is maintained where the downstream viscosity is high. It is necessary to increase the opening of the filter, to increase the filter filtration area and piping, etc., and to receive high shear when passing through the fluid, so it is inevitable that PBT deteriorates due to shear heat generation. . Therefore, the position of the filter is selected so that the intrinsic viscosity of PBT or its precursor is usually 0.10 to 1.20, preferably 0.20 to 1.00, and more preferably 0.50 to 0.90. Is done.

  The filter medium constituting the filter may be any of a metal wind, a laminated metal mesh, a metal nonwoven fabric, a porous metal plate, etc., but from the viewpoint of filtration accuracy, a laminated metal mesh or a metal nonwoven fabric is preferable, and in particular, the mesh opening is large. Those fixed by a sintering process are preferred. The shape of the filter may be any type such as basket type, disc type, leaf disc type, tube type, flat cylindrical type, pleated cylindrical type, and the like. In order not to affect the operation of the plant, it is preferable to install a plurality of filters so that they can be switched and used, or to install an auto screen changer.

  The absolute filtration accuracy of the filter is not particularly limited, but is usually 0.5 to 200 μm, preferably 1 to 100 μm, more preferably 5 to 50 μm, and particularly preferably 10 to 30 μm. If the absolute filtration accuracy is too large, the effect of reducing foreign matters in the product is lost, and if it is too small, productivity is lowered and filter replacement frequency is increased. The absolute filtration accuracy indicates a minimum particle size when the filter is completely removed by filtration when a filtration test is performed using a standard particle size product such as glass beads having a known and uniform particle size.

  Hereinafter, preferred embodiments of a method for producing PBT will be described with reference to the accompanying drawings. FIG. 1 is an explanatory diagram of an example of an esterification reaction step or transesterification reaction step employed in the present invention, and FIG. 2 is an explanatory diagram of an example of a polycondensation step employed in the present invention.

  In FIG. 1, terephthalic acid as a raw material is usually mixed with 1,4-butanediol in a raw material mixing tank (not shown), and supplied to the reaction tank (A) in the form of slurry from the raw material supply line (1). The On the other hand, when the raw material is a dialkyl terephthalate, it is usually supplied to the reaction vessel (A) as a molten liquid independently of 1,4-butanediol. Further, the titanium catalyst is preferably supplied from a catalyst supply line (3) after being made into a solution of 1,4-butanediol in a catalyst adjustment tank (not shown). FIG. 1 shows a mode in which a catalyst supply line (3) is connected to a recycle line (2) for recycle 1,4-butanediol, and both are mixed and then supplied to the liquid phase part of the reaction tank (A). It was.

  The gas distilled from the reaction tank (A) is separated into a high-boiling component and a low-boiling component in the rectifying column (C) through the distillation line (5). Usually, the main component of the high boiling component is 1,4-butanediol, and the main components of the low boiling component are water and THF in the case of the direct polymerization method.

  The high-boiling components separated in the rectification column (C) are extracted from the extraction line (6) and partly circulated from the recirculation line (2) to the reaction tank (A) via the pump (D). , Part is returned from the circulation line (7) to the rectification column (C). Further, the surplus is extracted outside from the extraction line (8). On the other hand, the light boiling components separated in the rectification column (C) are extracted from the gas extraction line (9), condensed in the condenser (G), and temporarily passed through the condensate line (10) to the tank (F). Accumulated. A part of the light boiling components collected in the tank (F) is returned to the rectification column (C) through the extraction line (11), the pump (E) and the circulation line (12), and the remainder is extracted. It is extracted outside through the line (13). The condenser (G) is connected to an exhaust device (not shown) via a vent line (14). The oligomer produced | generated within the reaction tank (A) is extracted through an extraction pump (B) and an extraction line (4).

  In the process shown in FIG. 1, the catalyst supply line (3) is connected to the recirculation line (2), but both may be independent. Moreover, the raw material supply line (1) may be connected to the liquid phase part of the reaction vessel (A).

  In FIG. 2, the oligomer supplied from the above-described extraction line (4) shown in FIG. 1 is polycondensed under reduced pressure in the first polycondensation reaction tank (a) to become a prepolymer, and then extracted. It is supplied to the second polycondensation reaction tank (d) through the gear pump (c) and the extraction line (L1). In the second polycondensation reaction tank (d), polycondensation usually proceeds at a lower pressure than that of the first polycondensation reaction tank (a) to become a polymer. The obtained polymer is supplied to the third polycondensation tank (k) through the extraction gear pump (e) and the extraction line (L3). The third polycondensation reaction tank (k) is a horizontal reaction tank composed of a plurality of stirring blade blocks and equipped with a biaxial self-cleaning type stirring blade. The polymer introduced into the third polycondensation reaction tank (k) from the second polycondensation reaction tank (d) through the extraction line (L3) is further subjected to polycondensation here, and then the extraction gear pump (m ) And the extraction line (L5), and is extracted from the die head (g) in the form of a melted strand, cooled with water, and then cut with a rotary cutter (h) to form pellets. Reference numerals (L2), (L4), and (L6) denote vent lines of the first polycondensation reaction tank (a), the second polycondensation reaction tank (d), and the third polycondensation reaction tank (k), respectively. .

  Next, the PBT pellet compound product according to the present invention will be described. The compound product of the present invention is characterized by using the aforementioned PBT pellets as at least a part of a forming raw material. Here, the compound product refers to a material obtained by kneading a plurality of raw materials, for example, reinforcing fillers such as glass fibers, carbon fibers, glass flakes, plasticizers, colorants, flame retardants and the like with PBT. . Such compound products are used, for example, as molding materials for parts such as home appliances / OA devices and automobiles.

  Examples of additives other than the above that are blended in compound products include, for example, stabilizers such as antioxidants, heat stabilizers, weather stabilizers, lubricants, mold release agents, catalyst deactivators, crystal nucleating agents, crystals Accelerators, ultraviolet absorbers, antistatic agents, foaming agents, impact resistance improvers and the like.

  If necessary, polyethylene, polypropylene, polystyrene, polyacrylonitrile, polymethacrylic acid ester, ABS resin, polycarbonate, polyamide, polyphenylene sulfide, polyethylene terephthalate, liquid crystal polyester, polyacetal, polyphenylene ether and other thermoplastic resins, phenol resins, A thermosetting resin such as a melamine resin, a silicone resin, or an epoxy resin can be blended. These thermoplastic resins and thermosetting resins can be used in combination of two or more.

  The blending method of the various fillers, additives, and resins is not particularly limited, but a single-screw or twin-screw extruder having equipment that can be devolatilized from the vent port is used as a kneader before molding. The method of manufacturing and the method of mixing each component at the time of shaping | molding are mentioned. In particular, when adopting a pre-manufactured method, the improvement effect of the present invention is great. Each component including an additional component may be supplied to the kneader in a lump or sequentially. The blending amount is appropriately selected according to the purpose of use of the compound product.

  The kneading temperature of the bound molded product is not particularly limited. However, if the kneading temperature is high, the color tone deteriorates, the terminal carboxyl group concentration increases, and the hydrolysis resistance deteriorates. Therefore, it is usually 270 ° C. or lower, preferably 265 ° C. ° C or lower, more preferably 260 ° C or lower. The combined product of the present invention has a small viscosity difference in the pellet that causes an increase or fluctuation in the load of the extruder in the raw material PBT. Therefore, even if kneading at a low temperature as described above, the load on the extruder Therefore, the manufacturing stability of the compound product, which has been difficult until now, and the prevention of thermal deterioration during kneading can be achieved.

  The manufacture of parts (molded products) such as the above-mentioned home appliances / OA devices and automobiles is performed by using the above-mentioned bound molded product as at least a part of the molding material and molding using an injection molding machine according to the present invention. Can be done. In this case, the melting temperature of the compound product (specifically, the melting temperature of the resin) is selected from the same range as described above. Further, as in the case of a method for producing a molded product using an extruder, which will be described later, a recycled material can be used as at least a part of the molding material.

  Next, the molded product of the PBT pellet according to the present invention will be described. The molded article of the present invention is characterized by using the aforementioned PBT pellets as at least a part of a molding raw material. Examples of the form of the molded product include a film, a sheet, and a filament. In the present invention, both the film and the sheet indicate a two-dimensionally expanded molded body, but the boundary thickness is 1/100 inch (0.254 mm). PBT often uses differently for this thickness.

  The manufacturing method of the film or sheet of this invention is not specifically limited, A well-known various method is employable. For example, a T die casting method, an air-cooled inflation method, a water-cooled inflation method, a calendar method, and the like can be given. Moreover, a multilayer film can also be obtained using a known multilayering apparatus (for example, a multi-manifold T die, a stack plate die, a feed block, a multilayer inflation die) or the like. These methods are applied after drying the PBT resin and, if necessary, mixing with other resins and additives such as a heat stabilizer.

  Furthermore, if necessary, a stretched film can be obtained by uniaxial or biaxial stretching according to a known method. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. Furthermore, a heat treatment process may be obtained to perform a film dimension stabilization process.

  The method for producing the filament of the present invention is not particularly limited. For example, in the case of a monofilament, the raw material resin is continuously supplied to a single-screw extruder, and continuously extruded from the nozzle at the tip while being melted. Usually, it is cooled and solidified with water or air at 3 to 50 ° C., preferably 5 to 20 ° C., to obtain an unstretched monofilament. At this time, if the temperature is too high, the molten resin crystallizes and is not preferably stretched or whitened. Subsequently, the monofilament is reheated in a medium (warm water, steam or air) tank set to a temperature near the glass transition temperature of the resin, preferably 40 to 280 ° C., and the drive installed before and after the tank Using the roll speed difference, the film is usually stretched 1.5 times or more, preferably 1.8 to 6 times. The stretching operation can be performed in multiple stages. In that case, it is preferable to set the stretching temperature higher as it goes downstream. Finally, in order to prevent post-shrinkage, the stretching temperature should be relaxed by several percent without stretching in a bath at 60 to 280 ° C. Is preferred.

  In the present invention, the molding temperature of the film, sheet and filament is not particularly limited. However, if the molding temperature is high, the color tone is deteriorated, the terminal carboxyl group concentration is increased, and the hydrolysis resistance is deteriorated. Hereinafter, it is preferably 265 ° C. or lower, more preferably 260 ° C. or lower. Since the molded product (film, sheet, filament) of the present invention does not contain a high-viscosity product that causes fish eyes in the raw material PBT, even when molded at low temperatures as described above, fish eyes are generated. Less, it is possible to achieve both the reduction of fish eyes, which has been difficult until now, and the prevention of thermal deterioration during molding.

  When producing the molded article of the present invention, conventional additives and the like can be blended as necessary. Such additives are not particularly limited, and examples thereof include various additives and resins described in the compound products. In addition, these blending methods are also the same as those described in the compound product.

Further, in the present invention, from the viewpoint of waste reduction, cost reduction, improvement effect of the present invention,
The product value generated at the time of manufacture represented by a part other than a molded product such as a runner or a spool, a film end or a sheet end generated when the compound product obtained by using the PBT pellet of the present invention is molded. It is preferable to mix and recycle parts that do not exist with raw materials and materials. At this time, the runners, spools, film edges, sheet edges, etc. may be recycled as they are, and there will be inconveniences in production, such as adversely affecting the feedability of raw materials and the screws of molding machines. When it occurs, processing such as granulation, cutting, and pulverization may be performed. Hereinafter, the portion to be recycled is referred to as a recycled material.

  The ratio of the recycled raw material to the raw material or material preferably satisfies the following formula (2), where A is the weight of all raw materials or all materials including the recycled raw material and C is the weight of the recycled raw material. In particular, it is recommended to satisfy the following formula (3), particularly the following formula (4).

  When the ratio of recycled materials is high, the color tone deteriorates, foreign matter increases, and the terminal carboxyl group concentration increases. When the ratio of recycled materials is low, the effects from the viewpoint of waste reduction and cost reduction are seen. It tends to disappear.

  The molded product of the present invention is not only greatly reduced in fish eyes derived from high-viscosity products, but also excellent in color tone, hydrolysis resistance, thermal stability, transparency, and moldability. These effects are great when raw materials are used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example at all unless the summary is exceeded. In addition, the measurement method of the physical property and evaluation item which were employ | adopted in the following examples is as follows.

(1) Esterification rate:
It calculated from the acid value and the saponification value by the following calculation formula (5). The acid value was obtained by dissolving the oligomer in dimethylformamide and titrating with a 0.1N KOH / methanol solution. The saponification value was determined by hydrolyzing the oligomer with a 0.5N KOH / ethanol solution and titrating with 0.5N hydrochloric acid.

(2) Intrinsic viscosity (IV):
It calculated | required in the following way using the Ubbelohde type viscometer. That is, using a mixed solution of phenol / tetrachloroethane (weight ratio 1/1) as a solvent, the number of seconds of dropping only the polymer solution having a concentration of 1.0 g / dL and the solvent was measured at 30 ° C., and the following formula (6) I asked more.

(3) Inherent viscosity difference (ΔIV) between the pellet center and the surface layer:
The operation of placing 20 g of PBT pellets in 200 mL of hexafluoroisopropanol and replacing it with fresh hexafluoroisopropanol over time was repeated 20 times to dissolve everything. At this time, hexafluoroisopropanol was removed from the solution obtained at the first time (fraction 1) and the solution obtained at the 20th time (fraction 20) with an evaporator and a vacuum dryer. It confirmed that the weight of obtained PBT was each less than 2g, measured each intrinsic viscosity, and calculated | required those differences.

(4) Titanium concentration in PBT:
PBT was wet-decomposed with high-purity sulfuric acid and nitric acid for electronic industry and measured using a high-resolution ICP (Inductively Coupled Plasma) -MS (Mass Spectrometer) (manufactured by ThermoQuest).

(5) Terminal carboxyl group concentration:
0.5 g of PBT was dissolved in 25 mL of benzyl alcohol and titrated using a 0.01 mol / L benzyl alcohol solution of sodium hydroxide.

(6) Terminal methoxycarbonyl group concentration and terminal vinyl group concentration:
About 100 mg of PBT was dissolved in 1 mL of a mixed solvent of deuterated chloroform / hexafluoroisopropanol = 7/3 (volume ratio), 36 μL of deuterated pyridine was added, and ¹ H-NMR was measured and determined at 50 ° C. For the NMR apparatus, “α-400” or “AL-400” manufactured by JEOL Ltd. was used.

(7) Solution haze:
After dissolving 2.70 g of PBT in 20 mL of a mixed solution of phenol / tetrachloroethane = 3/2 (weight ratio) at 110 ° C. for 30 minutes, the mixture was cooled in a constant temperature water bath at 30 ° C. for 15 minutes, and manufactured by Nippon Denshoku Co., Ltd. Using a photometer (NDH-300A), the turbidity of the solution was measured at a cell length of 10 mm. It shows that transparency is so favorable that a value is low.

(8) Pellet color tone:
A color difference meter (Z-300A type) manufactured by Nippon Denshoku Co., Ltd. was used, and the b value in the L, a, b color system was evaluated. A lower value indicates less yellowing and a better color tone.

(9) Formaldehyde generation amount:
1 g of PBT and 5 mL of an aqueous hydrochloric acid solution adjusted to pH = 2.29 were placed in a 10 mL headspace bottle and extracted with stirring at 120 ° C. for 1 hour. The solution was cooled and then filtered through a chromatodisc. Furthermore, about 3 g of this solution was precisely weighed, 0.2 mL of 0.25% 2,4-dinitrophenylhydrazine-6N hydrochloric acid solution and 1 mL of hexane were added and reacted at 50 ° C. for 20 minutes, and the hexane phase was subjected to gas chromatography. (Shimadzu Corporation "GC2010", column: "HP-5MS").

(10) Number of fisheye:
First, PBT was dried at 120 ° C. under a nitrogen atmosphere for 8 hours, and a film forming machine (model ME-20 / 26V2) manufactured by Optical Control Systems was used to obtain a film having a thickness of 50 μm. Cylinder and die temperatures were as shown in the examples and comparative examples. Next, the number of fish eyes of the obtained film was measured as follows. That is, the number of fish eyes exceeding 200 μm in size per 1 m ^{2 of the} film was measured using a Film Quality Testing System [Optical Control Systems, Inc., Type FS-5].

(11) ΔAV during molding:
The terminal carboxyl group density | concentration of the film obtained in said (10) was measured, and the raise of the terminal carboxyl group density | concentration before and behind shaping | molding (raw material pellet and film) was made into (DELTA) AV at the time of shaping | molding.

(12) Motor torque stability of the extruder:
The stability of the motor torque value (Nm) during film formation in (10) above was observed and evaluated. During film formation, the case where the torque variation was within 10% was evaluated as ◯ and the case where it exceeded 10% was evaluated as x.

Example 1:
Through the esterification step shown in FIG. 1 and the polycondensation step shown in FIG. 2, PBT was produced in the following manner. First, a 60 ° C. slurry mixed at a ratio of 1.80 moles of 1,4-butanediol with respect to 1.00 moles of terephthalic acid is passed through the raw material supply line (1) from the slurry preparation tank in advance with an esterification rate of 99. % Was continuously fed to a reaction tank (A) for esterification having a screw type stirrer filled with PBT oligomer at 40.0 kg / h. At the same time, the bottom component of the rectification column (C) at 185 ° C. is fed from the recirculation line (2) at 18.4 kg / h, and the catalyst feed line (3) is fed with 6. 5% of tetrabutyl titanate as the catalyst. A 0 wt% 1,4-butanediol solution was fed at 95 g / h (30 ppm by weight relative to the theoretical polymer yield). The water content in this solution was 0.20% by weight.

  The internal temperature of the reaction tank (A) is 230 ° C., the pressure is 78 kPa, and the produced water, THF and excess 1,4-butanediol are distilled from the distillation line (5), and the rectification column (C) It separated into a high boiling component and a low boiling component. The high-boiling component at the bottom of the column after the system has been stabilized is 98% by weight or more of 1,4-butanediol, and the extraction line (8) so that the liquid level of the rectifying column (C) is constant. A part of it was extracted outside. On the other hand, the low boiling component was extracted from the top of the column in the form of gas, condensed by the condenser (G), and extracted from the extraction line (13) to the outside so that the liquid level of the tank (F) was constant.

  A certain amount of the oligomer generated in the reaction tank (A) is extracted from the extraction line (4) using the pump (B) so that the average residence time of the liquid in the reaction tank (A) is 3.5 hours. The liquid level was controlled. The oligomer extracted from the extraction line 4 was continuously supplied to the first polycondensation reaction tank (a). After the system was stabilized, the esterification rate of the oligomer collected at the outlet of the reaction vessel (A) was 97.5%.

  The internal temperature of the first polycondensation reaction tank (a) was 245 ° C., the pressure was 2.1 kPa, and the liquid level was controlled so that the residence time was 90 minutes. An initial polycondensation reaction was performed while extracting water, THF, and 1,4-butanediol from a vent line (L2) connected to a decompressor (not shown). The extracted reaction liquid was continuously supplied to the second polycondensation reaction tank (d).

  The internal temperature of the second polycondensation reaction tank (d) is 241 ° C., the pressure is 150 Pa, the liquid level is controlled so that the residence time is 90 minutes, and a vent line (L4) connected to a decompressor (not shown). ), Polycondensation reaction was further carried out while extracting water, THF and 1,4-butanediol. The obtained polymer was continuously supplied to the third polycondensation reaction tank (k) via the extraction line (L3) by the extraction gear pump (e). The internal temperature of the third polycondensation reaction tank (k) was 238 ° C., the pressure was 140 Pa, the residence time was 90 minutes, and the polycondensation reaction was further advanced. The obtained polymer was continuously extracted in a strand form from the die head (g), and was cut with a rotary cutter (h). Using the PBT pellets thus obtained having an average intrinsic viscosity (average IV) of 1.00 dL / g, titanium content of 30 ppm by weight, and ΔIV of less than 0.01 dL / g, a film is formed at 250 ° C. And evaluated. A film having a small number of fish eyes and a good appearance was obtained. The results are summarized in Table 1.

Example 2:
In Example 1, the same as in Example 1, except that the internal temperature of the second polycondensation reaction tank (d) was 243 ° C., the pressure of the third polycondensation reaction tank (k) was 130 Pa, and the residence time was 100 minutes. went. The PBT pellets thus obtained having an average IV of 1.25 dL / g, a titanium content of 30 ppm by weight and ΔIV of less than 0.01 dL / g were molded at 250 ° C. and evaluated. A film having a small number of fish eyes and a good appearance was obtained. The results are summarized in Table 1.

Example 3:
In Example 1, the internal temperature of the second polycondensation reaction tank (d) was 244 ° C., the residence time was 80 minutes, the pressure of the third polycondensation reaction tank (k) was 130 Pa, and the residence time was 120 minutes. The same operation as in Example 1 was performed. The PBT pellets thus obtained having an average IV of 1.35 dL / g, a titanium content of 30 ppm by weight, and ΔIV of less than 0.01 dL / g were molded at 250 ° C. and evaluated. Despite the high average IV, a film with a small number of fish eyes and a good appearance was obtained. The results are summarized in Table 1.

Reference example 1 :
In Example 1, the amount of tetrabutyl titanate was 75 ppm by weight with respect to the theoretical polymer yield, the internal temperature of the second polycondensation reaction tank (d) was 242 ° C., the residence time was 80 minutes, and the third polycondensation reaction. The same procedure as in Example 1 was performed except that the pressure in the tank (k) was 130 Pa. Using PBT pellets having an average IV of 1.25 dL / g, a titanium content of 75 ppm by weight and a ΔIV of less than 0.01 dL / g, a film was molded at 250 ° C. and evaluated. A film having a small number of fish eyes and a good appearance was obtained. The results are summarized in Table 1.

Example 4 :
Using the PBT pellets of Example 2, films were formed at 265 ° C. and evaluated. A film having a small number of fish eyes and a good appearance was obtained. The results are summarized in Table 1.

Comparative Example 1:
In a 200 L stainless steel reaction vessel equipped with a turbine type stirring blade, dimethyl terephthalate (DMT) 272.9 mol, 1,4-butanediol 327.5 mol, tetrabutyl titanate 0.038 mol (theoretical yield as titanium amount) 30 ppm by weight per polymer) was charged and sufficiently substituted with nitrogen. Subsequently, the temperature of the system was raised, and after 60 minutes, at a temperature of 210 ° C. and atmospheric pressure under nitrogen, the produced methanol, 1,4-butanediol, and THF were distilled out of the system and subjected to a transesterification reaction for 2 hours ( The reaction start time was the time when a predetermined temperature and a predetermined pressure were reached).

  After transferring the oligomer obtained above to a stainless steel reactor having an internal volume of 200 L having a vent pipe and a double helical stirring blade, it was allowed to reach a temperature of 245 ° C. and a pressure of 100 Pa over 60 minutes. The polycondensation reaction was performed for 5 hours. After completion of the reaction, the polymer was extracted into a strand shape and cut into a pellet shape. The PBT pellets obtained in this way were charged into a double-cone jacketed solid-phase polymerization apparatus with an internal volume of 100 L, and vacuum / nitrogen replacement was repeated three times. Next, the pressure was controlled at 130 Pa, the temperature was raised to 200 ° C., sampling was performed with time, and the IV was checked, and when the IV finally reached 1.25, the solid phase polymerization was terminated. The amount of formaldehyde generated from this PBT was 0.8 ppm by weight. Using PBT pellets having an average IV of 1.25 dL / g, a titanium content of 30 ppm by weight and a ΔIV of 0.19 dL / g, the film was molded at 250 ° C. and evaluated. The number of fish eyes was large, resulting in a film with poor appearance. Moreover, the fluctuation | variation of the torque of an extruder was large. The results are summarized in Table 1.

Comparative Example 2:
Using the PBT pellet of Comparative Example 1, a film was formed at 280 ° C. and evaluated. The number of fish eyes in the film was slightly reduced as compared with Comparative Example 1, and the appearance defect was not eliminated. Moreover, the increase in the terminal carboxyl group concentration after molding was large. Moreover, the fluctuation | variation of the torque of an extruder was large. The results are summarized in Table 1.

Comparative Example 3:
In Comparative Example 1, the solid phase polymerization time was extended to obtain PBT having an average IV of 1.35 dL / g, a titanium content of 30 ppm by weight, and ΔIV of 0.24 dL / g. The amount of formaldehyde generated from this PBT was 0.7 ppm by weight. Using this PBT pellet pellet, a film was formed at 250 ° C. and evaluated. The number of fish eyes was more than that of Comparative Example 1, and the film had a poor appearance. Moreover, the fluctuation | variation of the torque of an extruder was large. The results are summarized in Table 1.

Comparative Example 4:
In Example 1, the amount of tetrabutyl titanate used was 100 ppm by weight relative to the theoretical polymer yield, the internal temperature of the second polycondensation reaction tank (d) was 240 ° C., and the residence time was 80 minutes. 1 was performed. The PBT pellets thus obtained having an average IV of 1.25 dL / g, a titanium content of 100 ppm by weight, and an ΔIV of less than 0.01 dL / g were molded at 250 ° C. and evaluated. The number of fish eyes was large, resulting in a film with poor appearance. The results are summarized in Table 1.

Example 6:
70 parts by weight of PBT pellets used in Example 2 and 30 parts by weight of the pulverized and dried film (R0) obtained in Example 2 were blended, and a film was formed in the same manner as in Example 2. Next, 30 parts by weight of the once recycled raw material-containing film (R1) and 70 parts by weight of the PBT pellets used in Example 2 were blended, and a film was formed by the same method as in Example 2 (R2). This operation was repeated to obtain a film (R4) containing a recycled material three times. Thus, even if the operation of mixing the recycled materials was repeated, a good quality PBT film was obtained. The results are summarized in Table 2.

Comparative Example 5:
Using the PBT pellets of Comparative Example 1, a film (R4) containing a recycled material three times was obtained in the same manner as in Example 6. Only the PBT film having a large increase in the terminal carboxyl group concentration, having many fish eyes and inferior in color tone and strength was obtained. The results are summarized in Table 2.

Explanatory drawing of an example of the esterification reaction process or transesterification process employed in the present invention Explanatory drawing of an example of the polycondensation process employ | adopted by this invention

Explanation of symbols

1: Raw material supply line 2: Recirculation line 3: Catalyst supply line 4: Extraction line 5: Distillation line 6: Extraction line 7: Circulation line 8: Extraction line 9: Gas extraction line 10: Condensate line 11: Extraction line 12: Circulation line 13: Extraction line 14: Vent line
A: Reaction tank B: Extraction pump C: Rectification tower D, E: Pump F: Tank G: Capacitors L1, L3, L5: Extraction lines L2, L4, L6: Vent line a: First polycondensation reaction tank d: second polycondensation reaction tank k: third polycondensation reaction tank c, e, m: extraction gear pump g: die head h: rotary cutter

Claims (18)

A pellet made of polybutylene terephthalate containing titanium, the amount of which is 90 ppm by weight or less as titanium atoms, the terminal methoxycarbonyl group concentration is 0.5 μeq / g or less , and the solution haze is 5% or less. The polybutylene terephthalate pellets have an average intrinsic viscosity of 0.90 to 2.00 dL / g and a difference in intrinsic viscosity between the center portion and the surface layer portion of the pellet of 0.10 dL / g or less.
(However, the solution haze is the turbidity value of a solution obtained by dissolving 2.7 g of polybutylene terephthalate in 20 mL of a phenol / tetrachloroethane mixed solution (weight ratio 3/2).)   The polybutylene terephthalate pellet according to claim 1, wherein the pellet has an average intrinsic viscosity of 1.10 to 1.40 dL / g.   The polybutylene terephthalate pellet according to claim 1 or 2, wherein the titanium content of the polybutylene terephthalate is 50 ppm by weight or less.   The polybutylene terephthalate pellet according to any one of claims 1 to 3, wherein the terminal carboxyl group concentration of the polybutylene terephthalate is 0.1 to 50 µeq / g.   The polybutylene terephthalate pellet according to any one of claims 1 to 4, wherein the terminal vinyl group concentration of the polybutylene terephthalate is 0.1 to 15 µeq / g. The polybutylene terephthalate pellet according to any one of claims 1 to 5 , wherein a difference in intrinsic viscosity between the center portion and the surface layer portion of the pellet is 0.05 dL / g or less. A compound product comprising the polybutylene terephthalate pellets according to any one of claims 1 to 6 as at least a part of a raw material. A method for producing a compound product, wherein the polybutylene terephthalate pellets according to any one of claims 1 to 6 are used as at least a part of a raw material and kneaded using an extruder. The manufacturing method according to claim 8 , wherein the temperature of the kneading resin by the extruder is 270 ° C or lower. A molded product comprising the compound product of claim 7 in at least a part of the molding material. A method for producing a molded product, wherein the compound product according to claim 7 is used as at least a part of the molding material and is molded using an injection molding machine. The manufacturing method according to claim 11 , wherein the molten resin temperature at the time of molding is 270 ° C. or less. The production method according to claim 11 or 12 , wherein a recycled material is used as at least a part of the molding material. A molded article comprising the polybutylene terephthalate pellet according to any one of claims 1 to 6 as at least a part of a raw material. Moldings, films, molded article according to claim 1 4 is a sheet or filament. A method for producing a molded product, characterized in that the polybutylene terephthalate pellets according to any one of claims 1 to 6 are used as at least a part of a raw material, and are molded using an extruder. The manufacturing method according to claim 16 , wherein a molten resin temperature at the time of molding is 270 ° C or lower. The manufacturing method of Claim 16 or 17 which uses a recycled raw material as at least one part of a raw material.

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